/*
This file is part of BGSLibrary.

BGSLibrary is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

BGSLibrary is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with BGSLibrary.  If not, see <http://www.gnu.org/licenses/>.
*/
/* block.h */
/*
    Copyright 2001 Vladimir Kolmogorov (vnk@cs.cornell.edu), Yuri Boykov (yuri@csd.uwo.ca).

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    */
/*
  Template classes Block and DBlock
  Implement adding and deleting items of the same type in blocks.

  If there there are many items then using Block or DBlock
  is more efficient than using 'new' and 'delete' both in terms
  of memory and time since
  (1) On some systems there is some minimum amount of memory
  that 'new' can allocate (e.g., 64), so if items are
  small that a lot of memory is wasted.
  (2) 'new' and 'delete' are designed for items of varying size.
  If all items has the same size, then an algorithm for
  adding and deleting can be made more efficient.
  (3) All Block and DBlock functions are inline, so there are
  no extra function calls.

  Differences between Block and DBlock:
  (1) DBlock allows both adding and deleting items,
  whereas Block allows only adding items.
  (2) Block has an additional operation of scanning
  items added so far (in the order in which they were added).
  (3) Block allows to allocate several consecutive
  items at a time, whereas DBlock can add only a single item.

  Note that no constructors or destructors are called for items.

  Example usage for items of type 'MyType':

  ///////////////////////////////////////////////////
  #include "block.h"
  #define BLOCK_SIZE 1024
  typedef struct { int a, b; } MyType;
  MyType *ptr, *array[10000];

  ...

  Block<MyType> *block = new Block<MyType>(BLOCK_SIZE);

  // adding items
  for (int i=0; i<sizeof(array); i++)
  {
  ptr = block -> New();
  ptr -> a = ptr -> b = rand();
  }

  // reading items
  for (ptr=block->ScanFirst(); ptr; ptr=block->ScanNext())
  {
  printf("%d %d\n", ptr->a, ptr->b);
  }

  delete block;

  ...

  DBlock<MyType> *dblock = new DBlock<MyType>(BLOCK_SIZE);

  // adding items
  for (int i=0; i<sizeof(array); i++)
  {
  array[i] = dblock -> New();
  }

  // deleting items
  for (int i=0; i<sizeof(array); i+=2)
  {
  dblock -> Delete(array[i]);
  }

  // adding items
  for (int i=0; i<sizeof(array); i++)
  {
  array[i] = dblock -> New();
  }

  delete dblock;

  ///////////////////////////////////////////////////

  Note that DBlock deletes items by marking them as
  empty (i.e., by adding them to the list of free items),
  so that this memory could be used for subsequently
  added items. Thus, at each moment the memory allocated
  is determined by the maximum number of items allocated
  simultaneously at earlier moments. All memory is
  deallocated only when the destructor is called.
  */
#pragma once

#include <stdlib.h>
#include <stdio.h>

/***********************************************************************/
/***********************************************************************/
/***********************************************************************/

namespace ck
{
template <class Type> class Block
{
public:
  /* Constructor. Arguments are the block size and
       (optionally) the pointer to the function which
       will be called if allocation failed; the message
       passed to this function is "Not enough memory!" */
  Block(int size, void(*err_function)(char *) = NULL) { first = last = NULL; block_size = size; error_function = err_function; }

  /* Destructor. Deallocates all items added so far */
  ~Block() { while (first) { block *next = first->next; delete first; first = next; } }

  /* Allocates 'num' consecutive items; returns pointer
       to the first item. 'num' cannot be greater than the
       block size since items must fit in one block */
  Type *New(int num = 1)
  {
    Type *t;

    if (!last || last->current + num > last->last)
    {
      if (last && last->next) last = last->next;
      else
      {
        block *next = (block *) new char[sizeof(block) + (block_size - 1)*sizeof(Type)];
        if (!next) { fprintf(stderr, "Not enough memory!"); exit(1); }
        if (last) last->next = next;
        else first = next;
        last = next;
        last->current = &(last->data[0]);
        last->last = last->current + block_size;
        last->next = NULL;
      }
    }

    t = last->current;
    last->current += num;
    return t;
  }

  /* Returns the first item (or NULL, if no items were added) */
  Type *ScanFirst()
  {
    scan_current_block = first;
    if (!scan_current_block) return NULL;
    scan_current_data = &(scan_current_block->data[0]);
    return scan_current_data++;
  }

  /* Returns the next item (or NULL, if all items have been read)
       Can be called only if previous ScanFirst() or ScanNext()
       call returned not NULL. */
  Type *ScanNext()
  {
    if (scan_current_data >= scan_current_block->current)
    {
      scan_current_block = scan_current_block->next;
      if (!scan_current_block) return NULL;
      scan_current_data = &(scan_current_block->data[0]);
    }
    return scan_current_data++;
  }

  /* Marks all elements as empty */
  void Reset()
  {
    block *b;
    if (!first) return;
    for (b = first;; b = b->next)
    {
      b->current = &(b->data[0]);
      if (b == last) break;
    }
    last = first;
  }

  /***********************************************************************/

private:

  typedef struct block_st
  {
    Type					*current, *last;
    struct block_st			*next;
    Type					data[1];
  } block;

  int		block_size;
  block	*first;
  block	*last;

  block	*scan_current_block;
  Type	*scan_current_data;

  void(*error_function)(char *);
};

/***********************************************************************/
/***********************************************************************/
/***********************************************************************/

template <class Type> class DBlock
{
public:
  /* Constructor. Arguments are the block size and
       (optionally) the pointer to the function which
       will be called if allocation failed; the message
       passed to this function is "Not enough memory!" */
  DBlock(int size, void(*err_function)(char *) = NULL) { first = NULL; first_free = NULL; block_size = size; error_function = err_function; }

  /* Destructor. Deallocates all items added so far */
  ~DBlock() { while (first) { block *next = first->next; delete first; first = next; } }

  /* Allocates one item */
  Type *New()
  {
    block_item *item;

    if (!first_free)
    {
      block *next = first;
      first = (block *) new char[sizeof(block) + (block_size - 1)*sizeof(block_item)];
      if (!first) { fprintf(stderr, "Not enough memory!"); exit(1); }
      first_free = &(first->data[0]);
      for (item = first_free; item < first_free + block_size - 1; item++)
        item->next_free = item + 1;
      item->next_free = NULL;
      first->next = next;
    }

    item = first_free;
    first_free = item->next_free;
    return (Type *)item;
  }

  /* Deletes an item allocated previously */
  void Delete(Type *t)
  {
    ((block_item *)t)->next_free = first_free;
    first_free = (block_item *)t;
  }

  /***********************************************************************/

private:

  typedef union block_item_st
  {
    Type			t;
    block_item_st	*next_free;
  } block_item;

  typedef struct block_st
  {
    struct block_st			*next;
    block_item				data[1];
  } block;

  int			block_size;
  block		*first;
  block_item	*first_free;

  void(*error_function)(char *);
};
}
